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  • 1
    Electronic Resource
    Electronic Resource
    New clues to the pathophysiology of hepatorenal failure (1993)
    Springer
    Journal of molecular medicine 71 (1993), S. 93-97 
    Details
    ISSN: 1432-1440
    Keywords: Liver ; Kidney ; Nitroxide ; Substance P ; Hepatorenal reflex ; Glomerulopressin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In patients with advanced liver disease, decreases in renal blood flow, glomerular filtration rate, and urinary output are frequently observed. The deterioration in renal function is usually not due to a unique cause but is the result of the concerted action of several mechanisms operating in parallel; decreased plasma protein formation and increased intrahepatic vascular resistance lead to sequestration of blood volume, favoring hypovolemia and reduction in cardiac output. At the same time enhanced formation of nitroxide leads to peripheral vasodilation; bacterial endotoxin escaping clearance by the diseased liver stimulates the expression of a long-acting nitroxide synthase. Furthermore, vasodilating intestinal mediators such as substance P escape inactivation by the liver. In the face of peripheral vasodilation the maintenance of blood pressure requires an increase in cardiac output, which is achieved by activation of sympathetic nervous tone, renal vasoconstriction, enhanced release of renin, angiotensin, aldosterone, and antidiuretic hormone, leading to renal retention of sodium and water. Renal vasoconstriction is opposed by vasodilatatory prostaglandins, and renal failure may be triggered by inhibition of prostaglandin formation. On the other hand, vasoconstrictive eicosanoids, such as thromboxane B2 and leukotriene E2, which escape hepatic inactivation, may contribute to renal vasoconstriction. Beyond these mechanisms disturbed hepatic regulation of renal function may participate in the generation of hepatorenal syndrome. The liver regulates renal function via both a hepatorenal reflex decreasing renal blood flow and a hypothetical liver-borne diuretic factor increasing renal blood flow. Both enhanced hepatorenal reflex activity and decreased formation of the liver-borne diuretic factor could participate in the pathogenesis of hepatorenal syndrome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00179987
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  • 2
    Electronic Resource
    Electronic Resource
    Caries susceptibility and renal excretion of calcium (1992)
    Springer
    Journal of molecular medicine 70 (1992), S. 735-739 
    Details
    ISSN: 1432-1440
    Keywords: Kidney ; Calcium ; Phosphate ; Sodium ; Caries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Clearance studies were performed for 2 days in two groups of age-matched young female volunteers: those with low caries prevalence and those with high caries prevalence. Both groups were kept on a low-calcium diet for 1 week and received 0.5 g calcium at the beginning of the second day. In both groups, glomerular filtration rate, urinary flow rate and renal excretions of sodium, calcium, and phosphate were subject to significant circadian variations. In both groups the administration of calcium led to a significant increase in renal excretion of sodium and calcium and a significant decrease in that of phosphate. On the first day, calcium excretion was significantly greater in those with low caries prevalence than in those with high caries prevalence, pointing to altered calcium homeostasis in this group.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00180739
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of ouabain and temperature on cell membrane potentials in isolated perfused straight proximal tubules of the mouse kidney (1986)
    Springer
    Pflügers Archiv 407 (1986), S. 252-257 
    Details
    ISSN: 1432-2013
    Keywords: Proximal tubule ; Kidney ; K+ conductance ; Cell membrane potential ; Ouabain temperature ; Phlorizin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In isolated perfused segments of the mouse proximal tubule, the potential difference across the basolateral cell membrane (PDbl) was determined with conventional microelectrodes. Under control conditions with symmetrical solutions it amounted to −62±1 mV (n=118). The potential difference across the epithelium (PDte) was −1.7±0.1 mV (n=45). Transepithelial resistance amounted to 1.82±0.09 kΩ cm (n=28), corresponding to 11.4±0.6 Ω cm2. Increasing bath potassium concentration from 5 to 20 mmol/l depolarized PDbl by +24±1 mV (n=103), and PDte by +1.6±0.1 mV (n=19). Thus, the basolateral cell membrane is preferably conductive to potassium. Rapid cooling of the bath perfusate from 38°C to 10°C led to a transient hyperpolarization of PDbl from −60±1 to −65±1 mV (n=21) within 40 s followed by gradual depolarization by +18±1% (n=14) within 5 min. The transepithelial resistance increased significantly from 1.78±0.11 kΩ cm to 2.20±0.21 kΩ cm (n=15). Rapid rewarming of the bath to 38°C caused a depolarization from −61±2 mV (n=17) to −43±2 mV (n=16) within 15 s followed by a repolarization to −59±2 mV (n=10) within 40 s. Ouabain invariably depolarized PDbl. During both, sustained cooling or application of ouabain, the sensitivity of PDbl to bath potassium concentration decreased in parallel to PDbl pointing to a gradual decrease of potassium conductance. Phlorizin hyperpolarized the cell membrane from −59±2 to −66±1 mV (n=13), virtually abolished the transient hyperpolarization under cooling, and significantly reduced the depolarization after rewarming from +17±2 mV (n=16) to +9±3 mV (n=9). The present data indicate that the contribution of peritubular potassium conductance to the cell membrane conductance decreases following inhibition of basolateral (Na++K+)-ATPase. Apparently, cooling from 37° to 10°C does not only reduce (Na−+K+)-ATPase activity but in addition luminal sodium uptake mechanisms such as the sodium glucose cotransporter. As a result, cooling leads to an initial hyperpolarization of the cell followed by depolarization only after some delay.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00585299
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  • 4
    Electronic Resource
    Electronic Resource
    Handling of allantoin by the rat kidney (1975)
    Springer
    Pflügers Archiv 357 (1975), S. 201-207 
    Details
    ISSN: 1432-2013
    Keywords: Allantoin ; Uricase ; Kidney ; Clearance ; Micropuncture ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Renal excretion of allantoin was measured by tracer techniques. After injection of 2-C14 urate and H3 inulin, clearances of allantoin and inulin were measured and both proximal and distal tubules were micropunctured. In confirmation of earlier results 2-C14 urate injected into an intact animal is very rapidly converted to C14 allantoin: after 15 min more than 90% of urinary tracer is present as allantoin. It was further observed that 1) allantoin clearance is essentially identical with inulin clearance over a wide range of urine flows; 2) no net transport of allantoin occurs in either proximal or distal tubules. Clearly allantoin is handled by the rat kidney like inulin. The total excretion of filtered allantoin unlike that of filtered urate provides an easy and effective mechanism for animals possessing the enzyme uricase to dispose of their purine loads.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00585975
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  • 5
    Electronic Resource
    Electronic Resource
    In vivo studies on uricase activity in the rat (1974)
    Springer
    Pflügers Archiv 351 (1974), S. 323-330 
    Details
    ISSN: 1432-2013
    Keywords: Uricase ; Urate ; Allantoin ; Liver ; Kidney ; Microperfusion ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. In vivo uricase activity was tested in rats by injection of 2-C14 urate and measurement of the total C14 activity and the fractional activities of allantoin, allantoic acid and urea in samples of blood and urine. In control animals, 5 min after the injection, 70% of the plasma tracer was already present in the form of allantoin. No allantoic acid and urea were produced. Intestinectomy had no measurable influence on uricase activity. On the other hand, hepatectomy or ligation of the hepatic artery combined with subtotal viscerectomy did abolish uricase activity almost completely. 2. Following microinjections into proximal tubules of Ringer solution containing 2-C14 urate, urine samples during early recovery mainly contained labelled urate, whereas in later samples the fraction of labelled allantoin increased. About 12 min after the microinjection the urine of both kidneys contained equal amounts of tracer mainly in the form of allantoin. 3. When segments of proximal tubules were perfused with an equilibrium solution containing tracer amounts of C 14 urate, no urate was metabolized during its passage through the proximal tubule. 4. C 14 urate was offered from the peritubular capillaries and samples of tubular fluid were analyzed, Again, all the tracer in the tubular fluid was in the form of urate, indicating that urate is not oxidized when it is transported across the tubular cell. It is concluded from these results that: 1. The rat kidney has no significant uricase activity. 2. Urate transport in the kidney is not influenced by this enzyme. 3. The degradation of urate to allantoin takes place at extrarenal sites, mainly in the liver.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00593318
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